Patch dermatology refers to the study and treatment of skin lesions classified as patches. A patch, in dermatological terms, is a large, flat area of discoloration on the skin. It's defined as a macule—a circumscribed area of change in skin color—that's larger than 1 centimeter in diameter.
Understanding Patches
Patches are characterized by their:
- Size: Larger than 1cm in diameter.
- Shape: Typically well-defined or circumscribed.
- Texture: Flat; they don't raise above the skin's surface.
- Color: Can vary widely depending on the cause; they may be darker or lighter than the surrounding skin.
Examples of Patch-Type Skin Lesions
Numerous conditions can manifest as patches. Examples include:
- Freckles: Small, flat, brown spots.
- Flat moles: Non-raised pigmented lesions.
- Tattoos: Pigmented areas created by injecting ink into the skin.
- Port-wine stains: Congenital vascular malformations that appear as reddish-purple patches.
- Rashes associated with infectious diseases: Such as rubella, measles (although these can also include papules and plaques), and rickettsial infections.
- Allergic drug eruptions: Certain medications can cause flat, discolored skin patches as an allergic reaction.
Diagnosis and Treatment
Diagnosing the cause of a patch requires a thorough evaluation by a dermatologist. This may involve a physical examination, review of medical history, and potentially further testing like a skin biopsy. Treatment depends entirely on the underlying cause. For example, a port-wine stain might be treated with laser therapy, while an allergic reaction might be managed by stopping the offending medication.
